1. Technical Field
The subject invention relates generally to a mold ejection machine and more specifically, to a method and apparatus for separating mold plates from a preformed substrate or casting.
2. Background Art
By way of background, a molding assembly generally includes an upper and lower mold plate forming a mold cavity or molding surface therebetween. Generally, a casting is molded in the mold cavity between the upper and lower plates. Alternatively, a preformed substrate or preformed casting is positioned between the upper and lower mold plates and a material such as rubber or plastic is mold injected onto the preformed substrate or a surface or plurality of surfaces of the preformed substrate. As the injected material bonds to the substrate, it often additionally bonds to one or both of the mold plates forming the mold cavity. After the bonding is complete, the mold plates must be separated from the preformed substrate without damaging the bonded material.
As shown in the prior art FIG. 1, a typical mold assembly is shown including upper and lower mold plates and a preformed substrate positioned between the upper and lower mold plates. The substrate is embraced between the plates by a plurality of vise members spaced about the periphery of the plates. The upper mold plate includes a first and second plate member interconnected by a plurality of bolts spaced about the periphery of the plates. A mold cavity is formed between the upper mold plates and the lower mold plate for receiving the preformed substrate and a plurality of vanes on the preformed substrate. A rubber or plastic material is injected into the mold cavity and bonded about the inner and outer surfaces of the preformed substrate and the substrate vanes. The material, however, also tends to bond to upper mold plates. Therefore, the upper mold plates must be separated from the substrate without damaging the bonded surface material. The prior art mold assembly, FIG. 1, is disassembled by releasing the vise members from the mold plates to release the preformed substrate therebetween. The bolts interconnecting the first and second plate members of the upper mold plates are then manually released until the plate members may be separated. However, the lower plate member, in abutment with the substrate, remains bonded to the substrate due to the bonding of the injected surface material. Therefore, the plate member must be wedged or hammered from the substrate to separate the plate from the upper surface of the substrate. The manual separating process between the upper mold plate and preformed substrate is time consuming and often results in damage to the bonded surface material on the substrate. Thus, an apparatus and process is desirable to automatically separate the mold plates from the substrate without damaging the bonded surface material.
The U.S. Pat. No. 3,450,190 to Mittermaier et al, issued Jun. 17, 1969, discloses a mold casting apparatus for molding a casting and for separating the casting from an upper and lower mold plate. The apparatus includes a support structure supporting a plurality of lower mold plates forming a mold cavity. The lower mold plates are restrained against the support structure by a pair of clamps. A hydraulic pump extending from the support structure lowers an upper mold plate downwardly into the mold cavity and a mold casting is formed about the contour of the upper mold plate. As the upper mold plate is raised upwardly from the lower mold plate, a pair of rods abut against a stripper plate forcing the stripper plate against the casting. The stripper plate includes a plurality of stripper pins to engage the peripheral edge of the casting and press the casting from the mold plate as the stripper plate is forced against the casting. However, the apparatus is deficient in that it does not include means for restraining the mold casting against the support structure while the upper mold plate is removed.